Vibrator motor



y 1952 H. L. SNAVELY 2,595,718

VIBRATOR MOTOR Filed Jan. 8, 1949 Patented May 6, 1952 UNITED STATES PATENT OFFICE VIBRATOR MOTOR Harold L. Snavely, Oak Lawn, Ill.

Application January 8, 1949, Serial No. 69,959

8 Claims. 1

This invention relates generally to electrically driven vibrators and more particularly to an improved alternating current solenoid actuated vibrator.

The vibrator of this invention is primarily intended for low frequency alternating current although it will function with pulsating direct current. Nonpulsating direct current vibrators in which a solenoid is used to provide the power for vibrating or oscillating an armature usually comprise a solenoid, connected through a pair of switch contacts to a source of electric current, and a movable armature of magnetic material mounted so as to be within the field of said solenoid. The contact points are mechanically connected to the armature so as to open and close as the armature vibrates. The frequency of vibration of such devices depends entirely on mechanical factors such as the mass distribution of the armature with respect to the point about which it oscillates, the relative spacingof the contacts, their conditions and their distance from the point of oscillation. Consequently, the frequency of vibration is variable rather than constant.

Some alternating current vibrators operating on the direct current principle have been built, but these devices generally have not been successful except for frequencies substantially lower than the frequency of oscillation.

Most alternating current vibrators vibrate at a frequency of 120 cycles, due to the fact that the flux produced by the solenoid reaches a maximum value and falls to zero twice during each cycle.

More often than this the frequency is too high when it is desired to have the solenoid perform mechanical work. Accordingly, one object of this invention is to provide an alternating current solenoid actuated vibrator in which the armature vibrates at a constant frequency lower than twice the current frequency.

Another object is to provide a vibrator driven whipcord motor whose speed may be adjusted over a range but which is driven by a constant frequency vibrator.

A further object is to provide an alternating current vibrator having a single moving part, no switch contacts being employed which would be susceptible to wear.

A further object is to provide a solenoid vibrator which oscillates at a constant and unvarying rate in true harmonic motion held constant by the exciting voltage and whose armature is not bounced on the pole with each vibration.

A further object is to provide a vibrator unit 2 capable of driving whipcord or ratchet drive motors in which vibratory motion is transformed to a rotary motion at a low speed.

A further object is to provide an apparatus in which the backward stroke as well as the forward stroke is a power stroke, advantage being taken of the repelling force exerted on a short circuited turn in an alternating magnetic field as well as the attractive force.

Other additional objects and advantages of this invention will of course present themselves to those familiar with the art on reading the following specification in conjunction with the drawing and the appended claims.

In the drawing:

Fig. 1 is a front view of a preferred embodiment of the vibrator of this invention adapted to drive a whipcord motor;

Fig. 2 is a side view;

Fig. 3 is a view showing a modified embodiment of the vibrator adapted for driving an electric shaver;

Fig. 4 is a view showing another modification adapted to drive a ratchet motor;

Fig. 5 is a view of a vibrator adapted to actuate a bell clapper; and

Fig. 6 is a view of a whipcord motor driven by the vibrator of this invention and having an adjustment for varying the speed of rotation.

A fundamental concept of this invention is to provide a short circuited coil consisting of a single closed loop conductor on an armature which is supported with an alternating magnetic field of a solenoid, the armature being so constructed and mounted as to have a natural frequency of oscillation substantially the same as that of the exciting current. It has been discovered that when this combination is provided, the armature will vibrate at a constant frequency as determined by its mechanical construction, the frequency of vibration being controlled by the exciting current, and the repulsive force of the magnetic field on the shorted coil being utilized to produce a power back stroke.

Short circuiting coils have been used heretofore in conjunction with alternating current solenoids, but they have been used for an entirely different purpose, the purpose there being to eliminate vibration or hunting of the armature rather than to foster it.

A preferred embodiment ill of my invention is illustrated in Fig. 1. The vibrator H comprises a conventional coil I 2 wound about a U- shaped laminated core I3 and a laminated armature I 4. The ends of the core 13 preferably lie in the same plane and are squared off to form poles l and [6. The armature I4 is supported adjacent to the pole IS in a resilient element 11, preferably rubber, by a retainer 18 which is riveted to the core [3. The opposite end of the armature i4 is disposed so as to lie a slight distance away from the pole 15, the distance being substantially the same as the thickness of that portion of the resilient element l1 lying between the armature I4 and the pole 16.

The shorted coil preferably consists of a single continuous band of copper, and is disposed as closely as possible to the pole [5 so as to concentrate the flux produced by the induced current at the end of the armature I4 adjacent to the pole l5. In some instances the use of shorted coils of more than one turn has proved desirable.

The whipcord motor drive elements comprise a wheel or drum 2| fixed to a shaft 22 and a whipcord 23 which passes over the drum 2! in the conventional manner. One end of the cord 23 is attached to the movable end of the armature 14 by a bracket 24, and the other end is attached to a light leaf spring which may attach any convenient fixed point preferably the case or mounting plate (not shown) at the motor.

When an alternating current is passed through the coil 12 the apparatus functions as follows: The armature l4 commences to vibrate at its natural mechanical frequency which is preferably the same frequency as that of the exciting current, the iron therein being attracted toward the pole l5 and the shorted turn 20 being repelled so that an equilibrium is established. During each vibration the cord 23 is pulled in the counterclockwise direction (as shown in Fig. 1) and relaxed. When the armature I4 is moving towards the pole I5 the tension on the cord 23 is increased over the normal tension of the spring 25. During the time the armature is moving away from the pole l5, the cord 23, which is preferably a relatively stiff plastic monofilament, is forced upwardly out of contact with the drum the slack being taken up by the spring 25. Thus, a differential in tension as the cord moves in opposite directions is established, which produces a corresponding differential in the frictional force exerted on the periphery of the drum 2| and causes it to rotate in the counterclockwise direction at a slow speed.

The speed of rotation may be readily varied by changing the spring 25 for a spring which exerts a greater or lesser tension on the cord 23 or by changing the size of the drum 2|. For the highest efficiency it ismost expedient'to determine the proper size of the spring by trial and error. In the embodiment shown in Fig. 6 a cam is provided for the purpose of varying the tension on the spring to vary the speed of the motor.

With the exception of the cam 30, the embodiment shown in Fig. 6 is substantially the same as that described above. Another important difference, however, is the fact that the whipcord 23 is attached directly to the shorted turn 20a rather than to the armature [4, a projection being provided on the shorted turn 20a for this purpose. Thus, the need for the bracket 24 is eliminated. This latter modification may be employed with or without the speed. control cam 30, or to attach stiff membersrather than whipcords as in the embodiments shown in Figs. 3 and 4.

In Fig. 3 a modified embodiment is shown in which the armature I la is connected by a link member 26 to the cutting head 21 of an electric razor 28. The coil l2a is disposed on one arm of the U-shaped coil l3a but serves the same function as it would were it located at the bottom of the U. This device operates substantially the same as the preferred embodiment except that the vibrating motion is used as such to drive the cutter 21 instead of being transformed into rotary motion.

In Fig. 4 a ratchet type motor driven by the vibrator of this invention is shown. This motor is substantially identical with that of Fig. 1 except for the fact that a ratchet wheel 21a is substituted for the drum 2| and a stifi" member 23a is substituted for the whipcord 23. As the armature I4 vibrates this motion is transmitted to the ratchet wheel 2|a by the member 23a the ratchet wheel 21a being turned one tooth with each vibration. The armature i4 is preferably mounted in a block of rubber Ila as in the preferred embodiment. The resilience of the rubber causes it to be held in the proper spaced relation to the pole I5 so that it vibrates without striking the pole, no additional springs being required.

The embodiment [Eb shown in Fig. 5 is substantially the same as that of Fig. 3 in principle, except that the oscillation of the armature Mb is transmitted to a bell clapper 3lb which is disposed so as to strike against the pair of bells 32 as the armature Mb vibrates.

When the shorted turn is not used on an armature which has a natural vibration frequency other than twice that of the exciting current, it is practically impossible to achieve any degree of oscillation unless the armature is allowed to rebound or bounce on the pole piece or a resilance of vibrators provided with the short circuited secondary coils are not fully understood, but the following explanation is believed to be accurate and is included herein in order to better describe the invention.

When a shorted coil is subjected to an alternating magnetic flux, a repulsive force is established which tends to move the coil in such manner as to lengthen the flux path. This is apparently due to the induced current which flows in the shorted turn and tends to produce flux opposite in direction to the inducing flux. On the other hand, an iron armature tends to be drawn toward the pole when subjected to an alternating magnetic flux. Thus, by providing a shorted coil on the armature a state of balance or equilibrium is established between the repulsive and attractive forces. However, the balance is not static, for the magnitude of the forces involved varies with the current cycle in the primary winding and with the length of the air gap as determined by the position of the armature. Hence, an armature subjected to such alternating attractive and repulsive forces and having a natural vibration frequency near to that of the exciting current will oscillate at that frequency in much the same manner as a circuit which oscillates at its tuned frequency even though the exciting pulses occur at twice or half the frequency of the resonant frequency.

This invention has been described mainly as producing mechanical vibrations at the same frequency as the exciting current. But it is not limited to this frequency. By choosing mechanical combinations of springs and armatures and varying the size and mounting of the armatures it is possible to produce devices which vibrate at frequencies which are multiples or divisors of the exciting frequency the only limitation being in varying the frequency is that the amount of the flux variation and resulting force during a cycle must be sufficient to provide the force required to maintain vibration of the armature. Thus, within the range set forth it is possible to vary the frequency of oscillation stepwise to different harmonic values by varying the mechanical natural vibration period of the armature and the resilient means for moving it away from the pole.

Various changes and modifications in the described embodiments such as will present themselves to those familiar with the art may be made without departing from the spirit of this invention whose scope is commensurate with the following claims.

What is claimed is:

1. In a vibrator a U-shaped magnetic element, an armature disposed proximate to the ends of said element, a resilient mounting for one end of said armature supporting it adjacent to the end of the magnetic element, a shading pole for inducing flux in said element, and a spring for urging the other end of said armature away from the element, said spring being of such strength as to hold one end of the armature away from the element at all times so as to induce said armature to oscillate when the strength of the flux in said element is varied sinusoidally.

2. A vibrator comprising a U-shaped magnetic element, an armature disposed proximate to the ends of said element, a resilient mounting for one end of said armature supporting it adjacent the end of the magnetic element, and a shorted coil for inducing flux in said element, said mounting being so constructed and arranged as to hold said armature away from the magnetic element at all r times.

3. A vibrator comprising an iron core, means for producing an alternating magnetic flux in said core, a movable armature so disposed as to form with the core a substantially closed magnetic circuit, resilient means tending to increase the air gap in said magnetic circuit, and a loop of electrical conducting material surrounding one portion of said magnetic circuit, the mass distribution of said armature being such that it tends to oscillate at the same frequency as that of the alternating flux.

4. A motor comprising a magnetic U-shaped core, a movable armature connecting the ends of said core, means for producing an alternating flux in said core, an electrical conductor surrounding said armature, a member attached to said armature, and a ratchet wheel rotatably mounted so as to be driven by said member said armature oscillates.

5. A motor comprising an iron core, means for producing an alternating magnetic flux in said core, a movable armature so disposed as to form with the core a substantially closed magnetic circuit having an air gap, resilient means tending to maintain the air gap in said magnetic circuit, a ring of conducting material surrounding one portion of said magnetic circuit, a cord attached to said ring of conducting material through which said resilient means acts, and a rotatable drum over which said cord passes.

6. A motor comprising an iron core, means for producing an alternating magnetic flux in said core, a movable armature so disposed as to form with the core a substantially closed mag netic circuit having an air gap, means tending to maintain the air gap in said magnetic circuit, a ring of conducting material surrounding one portion of said magnetic circuit, a member attached to said armature, and a rotatably mounted ratchet wheel disposed at the end of said member to be driven thereby as said armature oscillates.

7. An electric motor comprising a magnetic core member, means for producing alternating flux fields in the core, a magnetically susceptible armature, means for resiliently mounting the armature on the core in the effective flux field produced by the core, said resilient means holding a free end of the armature out of contact with the core throughout its operation, and a member of electrically conductive material encircling said free end of the armature.

8. An electric motor comprising a coil, a magnetic core mounted within said coil and having two pole faces, a movable armature positioned adjacent to the pole faces, resilient means for pivotally supporting one end of said armature on one of said pole faces, said resilient means having such strength as to hold the armature away from the ploe faces at all times, and a shorted coil encircling the other end of said armature adjacent the other pole face.

HAROLD L. SNAVELY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 377,217 Thomson Jan. 31, 1888 1,098,834 Oliver -1 June 2, 1914 1,240,471 Miller Sept. 18, 1917 1,489,848 OLeary Apr. 8, 1924 1,522,260 OLeary Jan. 6, 1925 1,812,331 Frohlich June 30, 1931 1,946,132 Dawe Feb. 6, 1934 1,948,452 Young Feb. 20, 1934 2,036,917 Favre-Bulle Apr. 7, 1936 2,113,762 James Apr. 12, 1938 2,140,576 Fisher Dec. 20, 1938 2,261,813 Steinbach Nov. 4, 1941 2,264,531 Horni Dec. 2, 1941 

